Segmented Magnet and Method for Manufacturing the Same

Abstract

Disclosed is a segmented magnet which may adjust the application direction of a heavy rare earth element for grain boundary diffusion depending on the magnetization direction of the segmented magnet so as to simplify the manufacturing process of the segmented magnet while reducing eddy current loss, and a method for manufacturing the same. The method includes preparing a plurality of permanent magnet parent bodies having a constant magnetization direction, diffusing a diffusion material into the prepared permanent magnet parent bodies via a pair of planes thereof opposite each other and parallel to the magnetization direction along grain boundaries so as to form a pair of diffusing surfaces, preparing a permanent magnet assembly by stacking the permanent magnet parent bodies in a line such that the diffusing surfaces thereof face each other, and segmenting the permanent magnet assembly into a plurality of pieces along planes perpendicular to the magnetization direction.

What is claimed is: 
     
         1 . A segmented magnet formed by stacking a plurality of permanent magnet segments in a line, wherein:
 diffusing surfaces configured such that a diffusion material is diffused thereinto along grain boundaries are formed on a pair of planes of each of permanent magnet segments opposite each other and parallel to a magnetization direction; and   the permanent magnet segments are stacked in the line and bonded such that the diffusing surfaces thereof face each other.   
     
     
         2 . The segmented magnet according to  claim 1 , wherein the segment magnet is formed by cutting a permanent magnet assembly, acquired by stacking a plurality of permanent magnet parent bodies, each having the diffusing surfaces on a pair of planes thereof opposite each other and parallel to the magnetization direction, in a line such that the diffusing surfaces thereof face each other, along planes perpendicular to the magnetization direction. 
     
     
         3 . The segmented magnet according to  claim 1 , wherein a distance between a pair of the diffusing surfaces of each of the permanent magnet segments parallel to the magnetization direction is shorter than a distance between a pair of other planes of each of the permanent magnet segments perpendicular to the magnetization direction. 
     
     
         4 . The segmented magnet according to  claim 1 , wherein the permanent magnet segments are sintered magnets expressed by Formula 1 below,
   x % RE-y % B-z % TM-Bal.% Fe,  [Formula 1]
   wherein RE indicates a rare earth element, TM indicates a transition element, x is 28-25, y is 0.5-1.5, and z is 0-15.   
     
     
         5 . The segmented magnet according to  claim 4 , wherein the permanent magnet segments are NdFeB sintered magnets. 
     
     
         6 . The segmented magnet according to  claim 1 , wherein the diffusion material comprises a rare earth element. 
     
     
         7 . The segmented magnet according to  claim 6 , wherein the diffusion material is expressed by Formula 2 below,
   RETMX,  [Formula 2]
   wherein RE indicates the rare earth element, TM indicates a transition element, and X indicates at least one of hydrogen, oxygen or fluorine.   
     
     
         8 . The segmented magnet according to  claim 7 , wherein the diffusion material comprises 10 at % or more of the rare earth element. 
     
     
         9 . A method for manufacturing a segmented magnet, the method comprising:
 preparing a plurality of permanent magnet parent bodies having a constant magnetization direction by magnetizing the permanent magnet parent bodies in a designated direction;   diffusing a diffusion material into the prepared permanent magnet parent bodies via a pair of planes thereof opposite each other and parallel to the magnetization direction along grain boundaries so as to form a pair of diffusing surfaces;   preparing a permanent magnet assembly by stacking the permanent magnet parent bodies in a line such that the diffusing surfaces of the permanent magnet parent bodies face each other; and   segmenting the prepared permanent magnet assembly into a plurality of pieces along planes perpendicular to the magnetization direction.   
     
     
         10 . The method according to  claim 9 , wherein, in the preparing the permanent magnet parent bodies, each of the permanent magnet parent bodies is formed as a hexahedron having three pairs of planes opposite each other, and a distance between a pair of the diffusing surfaces of each of the permanent magnet parent bodies parallel to the magnetization direction is shorter than a distance between a pair of other planes of each of the permanent magnet parent bodies perpendicular to the magnetization direction. 
     
     
         11 . The method according to  claim 9 , wherein, in the preparing the permanent magnet parent bodies, the permanent magnet parent bodies are prepared by compacting magnet powder expressed by Formula 1 below into a compact, and then sintering the compact,
   x % RE-y % B-z % TM-Bal.% Fe,  [Formula 1]
   wherein RE indicates a rare earth element, TM indicates a transition element, x is 28-25, y is 0.5-1.5, and z is 0-15.   
     
     
         12 . The method according to  claim 9 , wherein, in the diffusing the diffusion material into the prepared permanent magnet parent bodies, the diffusion material is applied to diffusing surfaces formed on each of the prepared permanent magnet parent bodies, and the diffusion material is diffused into the permanent magnet parent bodies along grain boundaries by heat-treating the permanent magnet parent bodies. 
     
     
         13 . The method according to  claim 9 , wherein, in the diffusing the diffusion material into the prepared permanent magnet parent bodies, the diffusion material comprises 10 at % or more of a rare earth element. 
     
     
         14 . The method according to  claim 13 , wherein, in the diffusing the diffusion material into the prepared permanent magnet parent bodies, the diffusion material is expressed by Formula 2 below,
   RETMX,  [Formula 2]
   wherein RE indicates the rare earth element, TM indicates a transition element, and X indicates at least one of hydrogen, oxygen or fluorine.   
     
     
         15 . The method according to  claim 9 , wherein the diffusing the diffusion material into the prepared permanent magnet parent bodies comprises:
 applying the diffusion material to a pair of the diffusing surfaces formed on each of the prepared permanent magnet parent bodies; and   diffusing the diffusion material into the permanent magnet parent bodies along grain boundaries by heat-treating the permanent magnet parent bodies having the diffusion material applied to the diffusing surfaces thereof under a vacuum or inert gas atmosphere.